The physiological changes that accompany menopause are known to affect bone mass, especially in the lumbar spine, distal radius, and proximal femur. These sites are frequently used for bone mass measurement. We propose to extend our knowledge of effects on the skeleton to the cranial area and especially the periodontal region by quantification and determination of alveolar bone loss. Preliminary research investigating mandibular bone indicates the possibility of age and sex-related effects on mandibular bone loss. We hypothesize that the physiological changes occurring at menopause that cause accelerated bone loss in the postcranial (below the skull) skeleton act similarly upon periodontal alveolar bone. We further hypothesize that the beneficial effects of estrogen therapy reported for the postcranial skeleton will also be evident in the periodontal bone. To test these hypotheses, we will enroll 150 women, who are at least 2 years postmenopausal, into a prospective, double-blind, 4-year, longitudinal study in which bone mass of the periodontal bone and postcranial skeleton will be quantified, and comparisons will be made between patients receiving either estrogen or placebo therapy. At baseline and once per year thereafter, the following procedures will be performed on all patients: 7-film, vertical bitewing radiographic series; and quantitative densitometric bone scans (lumber spine, radius, and femur). Rates of bone loss at postcranial skeletal sites will be calculated from sequential density measures and compared with corresponding alveolar bone loss rates calculated from computerized digital images of bitewing radiographs. In addition, because alveolar bone loss can be caused by periodontal disease, full-mouth periodontal probing (the most commonly used measurement of past disease activity in clinical trials) will be performed and these measurements tested for interrelationships with alveolar bone loss. Knowledge that postmenopausal bone loss rates in the postcranial skeleton are interrelated with bone loss rates of the periodontal alveolar bone and that treatment with estrogen lessens such loss would greatly enhance our understanding of adult alveolar bone loss and could beneficially affects treatment selection aimed at preventing such loss.